With the development of the Internet network, huge multimedia services take emergence, and people's needs on mobile communication are not limited to telephone and message services. Currently, an application service is introduced into the multimedia services and has a feature that multiple users can receive the same data at the same time, for example, video on demand, television broadcast, video conference, online education, interactive game, etc.
An MBMS (Multimedia Broadcast Multicast Service) technology is put forward to use resources of a mobile network effectively. The MBMS is a point-to-multipoint service that one data source sends data to multiple users, and network resources can be shared through this service, including sharing resources of a mobile core network and an access network, especially sharing air interface resources, moreover, the MBMS in 3GPP can realize not only multicast and broadcast of message-type services of pure-text and low-rate, but also multicast and broadcast of multimedia services of high-rate.
Since the MBMS service is a service directed to the whole network, a same MBMS service may be established at different lower layer network element nodes. FIG. 1 is a flow chart of a method for synchronization processing of a MBMS service of multiple network elements in the prior art, which comprises the following processing.
Step S102, an upper layer network element sends MBMS service data packet(s) to respective lower layer network elements, and the service data packet(s) bears service data and carries timestamp information, data packet sequence number information, accumulated service data length information, etc. The upper layer network element marks one or more consecutive service data packets with same timestamp information, and the data packets marked with the same timestamp make up of a data burst or are referred to as a synchronization sequence.
Step S104, the lower layer network elements need to perform an RLC (Radio Link Control) protocol layer concatenation processing on the service data carried by the service data packets in a same data burst.
Step S105, the lower layer network elements sequentially send, at wireless interfaces, the services carried by service data packets marked by the timestamp in the same data burst from the time point indicated by the timestamp, since the above information transmitted by the upper layer network element to the respective lower layer network elements is completely consistent with each other, the respective lower layer network elements can perform completely consistent processing, thereby realizing synchronously sending of the MBMS service among cells of the respective lower layer network elements.
Currently, the timestamp information of each data packet can be set in the following two manners.
Manner 1: the upper layer network element marks a timestamp according to the time when it receives the service data packets, and service data packets received within a time interval with a specific length are marked with the same timestamp, wherein the time interval with the specific length is called as a synchronization sequence length.
Manner 2: the upper layer network element virtualizes the RLC protocol layer processing of the lower layer network elements, and marks the service data packets on which the RLC concatenation processing should be performed with the same timestamp according to the result of the virtualized RLC processing.
It can be seen that the timestamp is set depending on the time when the service data packets arrive at the upper layer network element, and thus the timestamp intervals of the service data packets cannot be determined.
One MBMS service can be transmitted at wireless interfaces in a manner of TDM (Time Division Multiplexing) to use a wireless interface channel, and the TDM manner comprises the following parameters: a TDM period, a TDM offset and a TDM repeat length. Specifically, one MBMS service is transmitted, within a TDM period it allocates, from the (TDM offset)th TTI and within consecutive TTIs (transmission time interval) in a number of TDM repeat length, wherein the TDM repeat period is no more than 9, and the length of the TTI that can be used by the MEMS service is 40 or 80 ms.
When data is transmitted by using the mode of the TDM, since the time of sending the MBMS service at the wireless interfaces is not consecutive, the timestamp information cannot directly correspond to a start time when the wireless interfaces can send the MBMS service. Moreover, the interval of adjacent timestamps are different with the interval of adjacent available transmitting time, it may happen that the intervals among multiple timestamps are shorter than the interval of the available transmitting time interval of the wireless interfaces, that is, different timestamp of different data bursts is within a last available transmitting time interval and a next available transmitting time interval, and thus the lower layer network elements belonging to a same upper layer network element cannot perform synchronized processing on the same data burst.